In color photographic materials used for appreciation, recording, and preservation of images, the demand for high image quality and improvement in rapid processability has increased progressively. As means of making the image quality of color photographic materials high, can be mentioned the addition of antihalation dyes or irradiation neutralizing dyes, the improvement of sharpness by decreasing the coating amount of gelatin. Further, there can be mentioned the improvement of color reproduction by using photographic couplers excellent in spectral absorption characteristics of the color-formed dyes obtained therefrom, and the prevention of undesired coloring due to residual color, for example, of dyes on the support or in the hydrophilic layer applied on the support.
As means of improving sharpness, which is required for making high the image quality of color photographic materials, generally, antihalation dyes and irradiation neutralizing dyes are used effectively.
The dyes used for such a purpose are required to have, for example, the following characteristics:
(1) the dyes are completely decolored or are easily dissolved out from the photographic material in the photographic processing steps, so that harmful coloring does not remain on the photographic material, PA1 (2) the dyes do not chemically affect harmfully, for example, the silver halide emulsion in the photographic material; e.g., they do not change the sensitivity of the silver halide emulsion or fog the silver halide emulsion, and PA1 (3) the dyes have proper spectral absorption suitable for the application purpose.
There have been made efforts to find photographic dyes that satisfy all of the above conditions and the following dyes are found: for example, oxonol dyes described, for example, in U.S. Pat. Nos. 3,469,985 and 4,078,933, and other azo dyes, anthraquinone dyes, arylidene dyes, styryl dyes, triarylmethane dyes, merocyanine dyes, and cyanine dyes.
Since these dyes are generally soluble in water, they diffuse eventually into all of the layers of the photographic material. Accordingly, to improve the sharpness of the intended dye image, a large amount of the dye must be added, taking the diffusion of the dye into all of the other layers into account. In this case, if a further increase of the rapidness of the photographic processing, as demanded in recent years, is taken into consideration, it is easily anticipated that coloring of the white background due to residual color of dyes and the like will increase.
If the amount of the dye to be added is decreased, on one hand the above coloring of the white background is decreased, while on the other hand the sharpness is deteriorated, which is contrary to high image quality of the color photographic material.
In contrast to the above method wherein a dye is used that will diffuse into all the layers, some methods wherein a specific hydrophilic colloid layer is selectively colored are suggested.
For example, in order to prevent a dye from diffusing, for example, JP-A ("JP-A" means unexamined published Japanese patent application) No. 65230/1975 describes a method wherein, as a mordant, a hydrophilic polymer containing a part charged oppositely to the dye ion is allowed to be present in the hydrophilic layer. However, although these methods are effective in preventing the dye molecules from diffusing, the rate of the dissolve-out at the time of photographic processing is made poor.
A means is disclosed, for example, in European Patent 0,276,566 A1 and WO 88-04794, wherein a dye is dispersed in a specific hydrophilic colloid layer and fixed there in the solid state.
However, in this case, again it was found that when the dye dispersion required to improve sharpness is added, the rate of the dissolve-out of the dye at the time of photographic processing is made poor.
In this case, also, although the rate of the dissolve-out can be made good by decreasing the amount of the added dye, the sharpness is made poor. This is contrary to the trend of making the image quality of color photographic material high.
As other means of improving sharpness, a method wherein colloidal silver in the form of fine particles is contained in a specific non-photosensitive hydrophilic colloid layer, and a method wherein a large amount of titanium oxide particles is contained in a water-resistant resin covering a reflective support substrate, as described in European Patent 337490 A, are known.
However, it was found that, in order to improve sharpness satisfactorily by these methods, a large amount of the colloidal silver or the white pigment is required to be added; and in addition a change in sensitivity due to coloring of the white background after photographic processing, or due to deterioration of the storage stability of the photographic material, occurs. Thus, a technique of satisfying all of the characteristics for making the image quality high has not yet been found.